Radiation Therapy Techniques and Treatment Planning for Breast Cancer, 2016
Radiotherapy is a key component of breast conservation therapy and serves an important role as ad... more Radiotherapy is a key component of breast conservation therapy and serves an important role as adjuvant therapy after mastectomy in select node-positive breast cancer. Over the past decade, many different modalities of radiotherapy delivery have evolved, with the common goal of improving target volume coverage while minimizing high radiation doses to the adjacent normal organs. One method of radiation delivery that has been increasingly utilized as a planning tool is intensitymodulated radiotherapy (IMRT). In contrast to three-dimensional (3D) conformal radiation therapy, which uses 2–5 static beams and wedges, intensity-modulated radiation therapy (IMRT) modulates the beam profi le and aims to produce a uniform dose distribution within the treated volume of the breast/chest wall while optimally sparing the adjacent critical organs. Randomized trials as well as studies performing dosimetric comparisons of IMRT vs. 3D conformal radiation in breast-conserved patients showed that tangential IMRT improves dose homogeneity in the breast and lowers dose to the contralateral breast and the heart [ 1 – 15 ]. These dosimetric gains have translated into a lower risk of acute skin toxicity [ 9 ] and improved long-term cosmetic outcome compared to patients treated with conventional techniques [ 10 , 11 ]. In this chapter, we will discuss different types of IMRT delivery for breast cancer, with respect to the number of beams, their arrangement, and type of optimization (inverse planning versus forward planning). We will also discuss a special type of IMRT called volumetric modulated arc therapy (VMAT) and describe its dosimetry and treatment delivery. The cumulative benefi ts of using VMAT in combination with breath-hold techniques to help reduce cardiac doses for left-sided breast cancer will also be addressed followed by a section on simulation and setup verifi cation for IMRT.
BACKGROUND AND PURPOSE To develop a novel deep learning algorithm of sequential analysis, Seq2Seq... more BACKGROUND AND PURPOSE To develop a novel deep learning algorithm of sequential analysis, Seq2Seq, for predicting weekly anatomical changes of lung tumor and esophagus during definitive radiotherapy, incorporate the potential tumor shrinkage into a predictive treatment planning paradigm, and improve the therapeutic ratio. METHODS AND MATERIALS Seq2Seq starts with the primary tumor and esophagus observed on the planning CT to predict their geometric evolution during radiotherapy on a weekly basis, and subsequently updates the predictions with new snapshots acquired via weekly CBCTs. Seq2Seq is equipped with convolutional long short term memory to analyze the spatial-temporal changes of longitudinal images, trained and validated using a dataset including sixty patients. Predictive plans were optimized according to each weekly prediction and made ready for weekly deployment to mitigate the clinical burden of online weekly replanning. RESULTS Seq2Seq tracks structural changes well: DICE between predicted and actual weekly tumor and esophagus were (0.83±0.10, 0.79±0.14, 0.78±0.12, 0.77±0.12, 0.75±0.12, 0.71±0.17), and (0.72 ± 0.16, 0.73 ±0.11, 0.75 ± 0.08,0.74 ±0.09, 0.72 ±0.14, 0.71 ± 0.14), respectively, while the average Hausdorff distances were within 2mm. Evaluating dose to the actual weekly tumor and esophagus, a 4.2Gy reduction in esophagus mean dose while maintaining 60Gy tumor coverage was achieved with the predictive weekly plans, compared to the plan optimized using the initial tumor and esophagus alone, primarily due to noticeable tumor shrinkage during radiotherapy. CONCLUSION It is feasible to predict the longitudinal changes of tumor and esophagus with the Seq2Seq, which could lead to improving the efficiency and effectiveness of lung adaptive radiotherapy.
Purpose-Locally advanced breast cancer patients with expander or implant reconstructions who requ... more Purpose-Locally advanced breast cancer patients with expander or implant reconstructions who require comprehensive postmastectomy radiotherapy (PMRT) can pose unique treatment planning challenges. Traditional 3D conformal techniques often result in large dose inhomogeneity throughout the treatment volumes, inadequate target coverage or excessive normal tissue doses. We have developed a VMAT planning technique without entering through the ipsilateral arm that produced adequate target volume coverage, excellent homogeneity throughout the target volume and acceptable doses to the normal structures. Materials and Methods-Twenty left sided and ten right sided patients with either ipsilateral or bilateral permanent implants or tissue expanders who received comprehensive PMRT between 10/2014 to 2/2016 were included in this study. Ten left sided cases used Deep-Inspiration-Breath-Hold (DIBH) technique, and others were free-breathing (FB). PTV included chestwall, IMNs, supraclavicular and axillary lymph nodes. A VMAT plan using 4 or 5 partial arcs with 6 MV photon beam avoiding entering through the ipsilateral arm was generated for each patient. Prescription dose was 50 Gy in 25 fractions. PTV coverage, maximum depth of IMNs, dose homogeneity and dose to the heart, lungs, thyroid, contralateral intact breast or implant, liver, stomach, left anterior descending artery, ipsilateral brachial plexus, esophagus, spinal cord and total MU were evaluated.
Journal of applied clinical medical physics / American College of Medical Physics, May 1, 2016
The presence of two intact lungs makes it challenging to reach a tumoricidal dose with hemithorac... more The presence of two intact lungs makes it challenging to reach a tumoricidal dose with hemithoracic pleural intensity-modulated radiation therapy (IMRT) in patients with malignant pleural mesothelioma (MPM) who underwent pleurectomy/decor-tications or have unresectable disease. We developed an anatomy-based model to predict attainable prescription dose before starting optimization. Fifty-six clinically delivered IMRT plans were analyzed regarding correlation of prescription dose and individual and total lung volumes, planning target volume (PTV), ipsilateral normal lung volume and ratios: contralateral/ipsilateral lung (CIVR); contralateral lung/PTV (CPVR); ipsilateral lung /PTV (IPVR); ipsilateral normal lung /total lung (INTLVR); ipsilateral normal lung/PTV (INLPVR). Spearman's rank correlation and Fisher's exact test were used. Correlation between mean ipsilateral lung dose (MILD) and these volume ratios and between prescription dose and single lung mean doses were studie...
Dose distributions of 192 Ir HDR brachytherapy in phantoms simulating water, bone, lung tissue, w... more Dose distributions of 192 Ir HDR brachytherapy in phantoms simulating water, bone, lung tissue, water-lung and bone-lung interfaces using the Monte Carlo codes EGS4, FLUKA and MCNP4C are reported. Experiments were designed to gather point dose measurements to verify the Monte Carlo results using Gafchromic film, radiophotoluminescent glass dosimeter, solid water, bone, and lung phantom. The results for radial dose functions and anisotropy functions in solid water phantom were consistent with previously reported data (Williamson and Li). The radial dose functions in bone were affected more by depth than those in water. Dose differences between homogeneous solid water phantoms and solid water-lung interfaces ranged from 0.6% to 14.4%. The range between homogeneous bone phantoms and bone-lung interfaces was 4.1% to 15.7%. These results support the understanding in dose distribution differences in water, bone, lung, and their interfaces. Our conclusion is that clinical parameters did not provide dose calculation accuracy for different materials, thus suggesting that dose calculation of HDR treatment planning systems should take into account material density to improve overall treatment quality.
Abstract Purpose The implementation and evaluation of an in‐house developed geometry optimization... more Abstract Purpose The implementation and evaluation of an in‐house developed geometry optimization (GO) software are described. The GO script provides optimal lesion clustering, isocenter placement, and collimator angle of each arc for cranial multi‐lesion stereotactic radiosurgery (SRS) volumetric modulated arc therapy (VMAT) planning. Materials and methods An Eclipse‐plugin program was developed to facilitate automatic plan geometry generation for multiple metastases SRS VMAT plans. A mixed, semi‐supervised exhaustive and k‐means clustering method is used to group lesions and place isocenters. The sum of squared euclidean distance (SSED) and the boundaries of lesions’ projection from beams’ eye view are used as supervised parameters to determine the optimal isocenter numbers. The collimator angle is optimized by minimizing the sum of the MLC opening area from all gantry angles for each arc. In all, 10 clinical cases treated during 2016–2017 were compared to plan quality of GO script generated plans. Paddick gradient index (GI), conformity index (CI), and local brain volume receiving 12 Gy (local V12 Gy) around each lesion were compared. Result For four cases, the number of isocenters was reduced in the GO plans. For four other cases, the GO plans had the same number of isocenters as their corresponding clinical plans but with different lesion grouping. The GO plans had significantly lower GI (4.1 ± 1.0 vs 4.4 ± 0.9, P < 0.0001) and local V12 Gy (5.1 ± 4.2 vs 5.5 ± 4.3 in cm3, P < 0.0001), but not significantly different mean normal brain dose or CI. The volume of normal brain receiving ≥6 Gy was significantly lower in the GO plans. The total time to run the GO script for each case was <2 min. Conclusion The GO software automates lesion grouping, isocenter placement, and the collimator angles for SRS VMAT planning. When tested on 10 cases, the GO script resulted in improved plan quality and shorter planning time when compared to the clinical SRS VMAT plans.
To develop a geometric atlas that can predict tumor shrinkage and guide treatment planning for no... more To develop a geometric atlas that can predict tumor shrinkage and guide treatment planning for non-small-cell lung cancer. To evaluate the impact of the shrinkage atlas on the ability of tumor dose escalation. The creation of a geometric atlas included twelve patients with lung cancer who underwent both planning CT and weekly CBCT for radiotherapy planning and delivery. The shrinkage pattern from the original pretreatment to the residual posttreatment tumor was modeled using a principal component analysis, and used for predicting the spatial distribution of the residual tumor. A predictive map was generated by unifying predictions from each individual patient in the atlas, followed by correction for the tumor's surrounding tissue distribution. Sensitivity, specificity, and accuracy of the predictive model for classifying voxels inside the original gross tumor volume were evaluated. In addition, a retrospective study of predictive treatment planning (PTP) escalated dose to the pr...
Radiation Therapy Techniques and Treatment Planning for Breast Cancer, 2016
Radiotherapy is a key component of breast conservation therapy and serves an important role as ad... more Radiotherapy is a key component of breast conservation therapy and serves an important role as adjuvant therapy after mastectomy in select node-positive breast cancer. Over the past decade, many different modalities of radiotherapy delivery have evolved, with the common goal of improving target volume coverage while minimizing high radiation doses to the adjacent normal organs. One method of radiation delivery that has been increasingly utilized as a planning tool is intensitymodulated radiotherapy (IMRT). In contrast to three-dimensional (3D) conformal radiation therapy, which uses 2–5 static beams and wedges, intensity-modulated radiation therapy (IMRT) modulates the beam profi le and aims to produce a uniform dose distribution within the treated volume of the breast/chest wall while optimally sparing the adjacent critical organs. Randomized trials as well as studies performing dosimetric comparisons of IMRT vs. 3D conformal radiation in breast-conserved patients showed that tangential IMRT improves dose homogeneity in the breast and lowers dose to the contralateral breast and the heart [ 1 – 15 ]. These dosimetric gains have translated into a lower risk of acute skin toxicity [ 9 ] and improved long-term cosmetic outcome compared to patients treated with conventional techniques [ 10 , 11 ]. In this chapter, we will discuss different types of IMRT delivery for breast cancer, with respect to the number of beams, their arrangement, and type of optimization (inverse planning versus forward planning). We will also discuss a special type of IMRT called volumetric modulated arc therapy (VMAT) and describe its dosimetry and treatment delivery. The cumulative benefi ts of using VMAT in combination with breath-hold techniques to help reduce cardiac doses for left-sided breast cancer will also be addressed followed by a section on simulation and setup verifi cation for IMRT.
BACKGROUND AND PURPOSE To develop a novel deep learning algorithm of sequential analysis, Seq2Seq... more BACKGROUND AND PURPOSE To develop a novel deep learning algorithm of sequential analysis, Seq2Seq, for predicting weekly anatomical changes of lung tumor and esophagus during definitive radiotherapy, incorporate the potential tumor shrinkage into a predictive treatment planning paradigm, and improve the therapeutic ratio. METHODS AND MATERIALS Seq2Seq starts with the primary tumor and esophagus observed on the planning CT to predict their geometric evolution during radiotherapy on a weekly basis, and subsequently updates the predictions with new snapshots acquired via weekly CBCTs. Seq2Seq is equipped with convolutional long short term memory to analyze the spatial-temporal changes of longitudinal images, trained and validated using a dataset including sixty patients. Predictive plans were optimized according to each weekly prediction and made ready for weekly deployment to mitigate the clinical burden of online weekly replanning. RESULTS Seq2Seq tracks structural changes well: DICE between predicted and actual weekly tumor and esophagus were (0.83±0.10, 0.79±0.14, 0.78±0.12, 0.77±0.12, 0.75±0.12, 0.71±0.17), and (0.72 ± 0.16, 0.73 ±0.11, 0.75 ± 0.08,0.74 ±0.09, 0.72 ±0.14, 0.71 ± 0.14), respectively, while the average Hausdorff distances were within 2mm. Evaluating dose to the actual weekly tumor and esophagus, a 4.2Gy reduction in esophagus mean dose while maintaining 60Gy tumor coverage was achieved with the predictive weekly plans, compared to the plan optimized using the initial tumor and esophagus alone, primarily due to noticeable tumor shrinkage during radiotherapy. CONCLUSION It is feasible to predict the longitudinal changes of tumor and esophagus with the Seq2Seq, which could lead to improving the efficiency and effectiveness of lung adaptive radiotherapy.
Purpose-Locally advanced breast cancer patients with expander or implant reconstructions who requ... more Purpose-Locally advanced breast cancer patients with expander or implant reconstructions who require comprehensive postmastectomy radiotherapy (PMRT) can pose unique treatment planning challenges. Traditional 3D conformal techniques often result in large dose inhomogeneity throughout the treatment volumes, inadequate target coverage or excessive normal tissue doses. We have developed a VMAT planning technique without entering through the ipsilateral arm that produced adequate target volume coverage, excellent homogeneity throughout the target volume and acceptable doses to the normal structures. Materials and Methods-Twenty left sided and ten right sided patients with either ipsilateral or bilateral permanent implants or tissue expanders who received comprehensive PMRT between 10/2014 to 2/2016 were included in this study. Ten left sided cases used Deep-Inspiration-Breath-Hold (DIBH) technique, and others were free-breathing (FB). PTV included chestwall, IMNs, supraclavicular and axillary lymph nodes. A VMAT plan using 4 or 5 partial arcs with 6 MV photon beam avoiding entering through the ipsilateral arm was generated for each patient. Prescription dose was 50 Gy in 25 fractions. PTV coverage, maximum depth of IMNs, dose homogeneity and dose to the heart, lungs, thyroid, contralateral intact breast or implant, liver, stomach, left anterior descending artery, ipsilateral brachial plexus, esophagus, spinal cord and total MU were evaluated.
Journal of applied clinical medical physics / American College of Medical Physics, May 1, 2016
The presence of two intact lungs makes it challenging to reach a tumoricidal dose with hemithorac... more The presence of two intact lungs makes it challenging to reach a tumoricidal dose with hemithoracic pleural intensity-modulated radiation therapy (IMRT) in patients with malignant pleural mesothelioma (MPM) who underwent pleurectomy/decor-tications or have unresectable disease. We developed an anatomy-based model to predict attainable prescription dose before starting optimization. Fifty-six clinically delivered IMRT plans were analyzed regarding correlation of prescription dose and individual and total lung volumes, planning target volume (PTV), ipsilateral normal lung volume and ratios: contralateral/ipsilateral lung (CIVR); contralateral lung/PTV (CPVR); ipsilateral lung /PTV (IPVR); ipsilateral normal lung /total lung (INTLVR); ipsilateral normal lung/PTV (INLPVR). Spearman's rank correlation and Fisher's exact test were used. Correlation between mean ipsilateral lung dose (MILD) and these volume ratios and between prescription dose and single lung mean doses were studie...
Dose distributions of 192 Ir HDR brachytherapy in phantoms simulating water, bone, lung tissue, w... more Dose distributions of 192 Ir HDR brachytherapy in phantoms simulating water, bone, lung tissue, water-lung and bone-lung interfaces using the Monte Carlo codes EGS4, FLUKA and MCNP4C are reported. Experiments were designed to gather point dose measurements to verify the Monte Carlo results using Gafchromic film, radiophotoluminescent glass dosimeter, solid water, bone, and lung phantom. The results for radial dose functions and anisotropy functions in solid water phantom were consistent with previously reported data (Williamson and Li). The radial dose functions in bone were affected more by depth than those in water. Dose differences between homogeneous solid water phantoms and solid water-lung interfaces ranged from 0.6% to 14.4%. The range between homogeneous bone phantoms and bone-lung interfaces was 4.1% to 15.7%. These results support the understanding in dose distribution differences in water, bone, lung, and their interfaces. Our conclusion is that clinical parameters did not provide dose calculation accuracy for different materials, thus suggesting that dose calculation of HDR treatment planning systems should take into account material density to improve overall treatment quality.
Abstract Purpose The implementation and evaluation of an in‐house developed geometry optimization... more Abstract Purpose The implementation and evaluation of an in‐house developed geometry optimization (GO) software are described. The GO script provides optimal lesion clustering, isocenter placement, and collimator angle of each arc for cranial multi‐lesion stereotactic radiosurgery (SRS) volumetric modulated arc therapy (VMAT) planning. Materials and methods An Eclipse‐plugin program was developed to facilitate automatic plan geometry generation for multiple metastases SRS VMAT plans. A mixed, semi‐supervised exhaustive and k‐means clustering method is used to group lesions and place isocenters. The sum of squared euclidean distance (SSED) and the boundaries of lesions’ projection from beams’ eye view are used as supervised parameters to determine the optimal isocenter numbers. The collimator angle is optimized by minimizing the sum of the MLC opening area from all gantry angles for each arc. In all, 10 clinical cases treated during 2016–2017 were compared to plan quality of GO script generated plans. Paddick gradient index (GI), conformity index (CI), and local brain volume receiving 12 Gy (local V12 Gy) around each lesion were compared. Result For four cases, the number of isocenters was reduced in the GO plans. For four other cases, the GO plans had the same number of isocenters as their corresponding clinical plans but with different lesion grouping. The GO plans had significantly lower GI (4.1 ± 1.0 vs 4.4 ± 0.9, P < 0.0001) and local V12 Gy (5.1 ± 4.2 vs 5.5 ± 4.3 in cm3, P < 0.0001), but not significantly different mean normal brain dose or CI. The volume of normal brain receiving ≥6 Gy was significantly lower in the GO plans. The total time to run the GO script for each case was <2 min. Conclusion The GO software automates lesion grouping, isocenter placement, and the collimator angles for SRS VMAT planning. When tested on 10 cases, the GO script resulted in improved plan quality and shorter planning time when compared to the clinical SRS VMAT plans.
To develop a geometric atlas that can predict tumor shrinkage and guide treatment planning for no... more To develop a geometric atlas that can predict tumor shrinkage and guide treatment planning for non-small-cell lung cancer. To evaluate the impact of the shrinkage atlas on the ability of tumor dose escalation. The creation of a geometric atlas included twelve patients with lung cancer who underwent both planning CT and weekly CBCT for radiotherapy planning and delivery. The shrinkage pattern from the original pretreatment to the residual posttreatment tumor was modeled using a principal component analysis, and used for predicting the spatial distribution of the residual tumor. A predictive map was generated by unifying predictions from each individual patient in the atlas, followed by correction for the tumor's surrounding tissue distribution. Sensitivity, specificity, and accuracy of the predictive model for classifying voxels inside the original gross tumor volume were evaluated. In addition, a retrospective study of predictive treatment planning (PTP) escalated dose to the pr...
Uploads
Books by Licheng Kuo
Papers by Licheng Kuo